Power steering apparatus of watercraft with propeller

ABSTRACT

In a power steering apparatus of a watercraft with propeller applying an assist torque of an assist motor driven in correspondence to a steering direction and a steering force of a steering handle to a steering force transmission path to the propeller, an output side of the assist motor is provided with an inverse input interrupting apparatus transmitting an assist torque of the assist motor to the steering force transmission path, and interrupting an inverse input torque applied to the steering force transmission path from a side of the propeller caused by a rotational reaction force of a screw provided in the propeller with respect to the assist.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power steering apparatus of a watercraft with a propeller such as an outboard motor, an inboard outboard motor and the like.

2. Description of the Related Art

In a power steering apparatus of a watercraft with outboard motor, there is a power steering apparatus structured to apply an assist torque of a motor-driven assist motor (or a motor-driven assist pump of a hydraulic power steering apparatus) driven in correspondence to a steering direction and a steering force of a steering handle to a steering force transmission path to the outboard motor, as described in Japanese Patent Application Laid-Open No. 2004-231108 (patent document 1). It is structured such as to assist a manual steering force applied by a watercraft steering person to the steering handle on the basis of the assist torque of the motor-driven assist motor.

In the watercraft with outboard motor, a rotational reaction force of a screw provided in the outboard motor steers a propelling unit, for example, in a rightward direction on the basis of a gyro effect. In the watercraft mentioned above, if the watercraft steering person loses hold of the steering handle for fishing or the like while the hull is traveling, the propelling unit is steered in the rightward direction mentioned above, and the hull can not maintain the previous traveling direction before release of the steering handle, for example, and therefore can not maintain a straight direction of motion.

On the other hand, in the case that the watercraft steering person keeps holding the steering handle for maintaining the traveling direction of the hull, the steering force is continually applied to the steering handle. In this case, the motor-driven assist motor carries on being driven in correspondence to the steering force applied to the steering handle, a power consumption of the assist motor becomes great, and a heat generation of the assist motor becomes large.

Further, in the watercraft with outboard motor, it is necessary to easily drive and steer the propelling unit at a time of failing of the motor-driven assist motor and a control unit thereof.

SUMMARY OF THE INVENTION

An object of the present invention is to simply suppress a gyro effect caused by a rotational reaction force of a screw provided in a propeller, in a power steering apparatus of a watercraft with propeller.

The other object of the present invention is to easily make it possible to drive and operate a propelling unit, at a failing time of an assist driving portion.

The present invention relates to a power steering apparatus of a watercraft with propeller, the power steering apparatus applying an assist torque of an assist driving portion driven in correspondence to a steering direction and a steering force of a steering handle to a steering force transmission path to the propeller. The apparatus is provided with an inverse input interrupting apparatus transmitting the torque assisting a steering by the assist driving portion to the steering force transmission path, and interrupting a torque applied to the steering force transmission path from a side of the propeller with respect to the assist driving portion.

A torque transmission disconnecting means is provided in an intermediate portion of the steering force transmission path between the assist driving portion and the propeller.

A worm reduction gear is interposed in the steering force transmission path in an output side of the assist driving portion. The worm reduction gear is formed by engaging a worm provided in a side of the assist driving portion, and a worm wheel provided in a side of the propeller. And an inverse input interrupting apparatus is constructed by the worm reduction gear, the inverse input interrupting apparatus transmitting the assist torque of the assist driving portion to the side of the propeller, and interrupting an inverse input torque applied to the steering force transmission path from the side of the propeller caused by a rotational reaction force of a screw provided in the propeller with respect to the assist driving portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood from the detailed description given below and from the accompanying drawings which should not be taken to be a limitation on the invention, but are for explanation and understanding only.

The drawings:

FIG. 1 is a schematic view showing a power steering apparatus of a watercraft with propeller in accordance with an embodiment 1;

FIG. 2 is a schematic view showing a steering assist apparatus in FIG. 1;

FIG. 3 is a cross sectional view showing an inverse input interrupting apparatus;

FIGS. 4A to 4C are schematic views showing a motion of the inverse input interrupting apparatus;

FIG. 5 is a schematic view showing a power steering apparatus of a watercraft with propeller in accordance with an embodiment 2;

FIG. 6 is a schematic view showing a steering assist apparatus in FIG. 5;

FIG. 7 is a schematic view showing a power steering apparatus of a watercraft with propeller in accordance with an embodiment 3;

FIG. 8 is a schematic view showing a power steering apparatus of a watercraft with propeller in accordance with an embodiment 4;

FIG. 9 is a schematic view showing a steering assist apparatus in FIG. 8;

FIG. 10 a schematic view showing a power steering apparatus of a watercraft with propeller in accordance with an embodiment 5;

FIG. 11 is a schematic view showing a steering assist apparatus in FIG. 10; and

FIG. 12 a schematic view showing a power steering apparatus of a watercraft with propeller in accordance with an embodiment 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 (FIGS. 1 to 4C)

A watercraft 1 shown in FIG. 1 has a steering handle 10 provided in a bow end of a hull 2, an outboard motor 20 serving as a propeller provided in a stern end of the hull 2, and a steering cable 30 serving as a steering force transmission path transmitting a steering force applied to the steering handle 10 to the outboard motor 20. The steering cable 30 is extended within an outer tube 31 installed in the stern end from the bow end in an inner portion of the hull 2.

The steering handle 10 is installed in a control seat in the bow end of the hull 2. A pinion 12 fixed to a handle shaft 11 of the steering handle 10 is engaged with a rack 13, and the rack 13 is coupled to one end of the steering cable 30. The steering handle 10 is rotated leftward or rightward on the basis of an application of a steering force (a steering torque), whereby the steering cable 30 is pushed and pulled via an engagement between the pinion 12 and the rack 13.

The outboard motor 20 is provided with a screw 22 in a propelling unit 21, and is structured such as to have an engine (not shown) mounted on the propelling unit 21, and a swivel bracket 23 and a clamp bracket 24. The propelling unit 21 is pivoted to the swivel bracket 23 via a steering shaft 23A (not shown) so as to oscillate in a horizontal direction and be capable of steering, and the swivel bracket 23 is pivoted to the clamp bracket 24 so as to be tiltable up and down in a vertical direction via a tilt shaft 24A (not shown). The outboard motor 20 is attached to a stern plate of the hull 2 by the clamp bracket 24, transmits an output of the engine to the screw 22, and makes the hull 2 movable forward and backward. The outboard motor 20 couples the other end of the steering cable 30 to a steering arm 21A firmly attached to the propelling unit 21 via links 25A and 25B.

In the watercraft 1, a steering assist apparatus 40 for constructing a power steering apparatus 3 assisting a steering force applied by a watercraft steering person to the steering handle 10 is interposed between the other end of the steering cable 30 and the steering arm 21A (the link 25B in the present embodiment) of the propelling unit 21, in the stern end in the inner portion of the hull 2.

The steering assist apparatus 40 is arranged within a gear case 41 fixed to the hull 2, as shown in FIG. 2. The steering assist apparatus 40 is structured such that a ball screw 42 is rotatably pivoted to the gear case 41, and a ball nut 43 is screwed to the ball screw 42. The ball nut 43 is prevented from rotating around a center axis of the ball screw 42 so as to linearly move along an axial direction of the ball screw 42, when the ball screw 42 is rotated, driving the ball nut 43. Front and rear arms 44A and 44B are integrated with the ball nut 43, the other end of the steering cable 30 is coupled to the front arm 44A of the ball nut 43, and the link 25B in a side of the propelling unit 21 is coupled to the rear arm 44B of the ball nut 43. Accordingly, if the steering handle 10 is rotated leftward or rightward on the basis of the application of the steering force, and the steering cable 30 is pushed and pulled, the ball nut 43 linearly moves along the axial direction of the ball screw 42, and the propelling unit 21 coupled to the ball nut 43 by the links 25A and 25B and the steering arm 21A is steered leftward or rightward.

The steering assist apparatus 40 is provided with a torque sensor 45 in the front arm 44A of the ball nut 43 within the gear case 41. The torque sensor 45 detects a steering direction and a steering torque applied by the watercraft steering person to the steering handle 10.

The steering assist apparatus 40 is structured such that an electric assist motor 50 serving as an assist driving portion is arranged within the gear case 41, and a pinion 51 provided in an output shaft of the assist motor 50 is engaged with a pinion 52 provided in the ball screw 42.

Further, the steering assist apparatus 40 is structured such that a control unit 60 controlling the assist motor 50 is arranged within the gear case 41. The control unit 60 loads a detection signal of the torque sensor 45, and a detection signal of a watercraft speed sensor (not shown) installed in the propelling unit 21 of the outboard motor 20, decides a driving direction and a driving current of the assist motor 50 from a predetermined assist map, and applies an assist torque of the assist motor 50 which becomes a suitable steering assist force corresponding to the watercraft speed, the steering direction and the steering torque to the ball screw 42 via the pinions 51 and 52. A rotating force of the ball screw 42 generated by the assist torque of the assist motor 50 assists a linear motion of the ball nut 43 generated by the steering force applied to the steering handle 10 mentioned above.

The steering assist apparatus 40 is provided in an output side of the assist motor 50 with an inverse input interrupting apparatus 70 transmitting the assist torque of the assist motor 50 to the steering force transmission path to the propelling unit 21, and interrupting an inverse input torque applied to the steering force transmission path from the side of the propelling unit 21 caused by the rotational reaction force of the screw 22 provided in the propelling unit 21 with respect to the assist motor 50. In the present embodiment, the ball screw 42 is separated into two sections including an input shaft 42A provided with the pinion 52, and an output shaft 42B to which the ball nut 43 is screw attached, and the mechanical inverse input interrupting apparatus 70 is provided between the input shaft 42A and the output shaft 42B.

The inverse input interrupting apparatus 70 has a retainer 71A serving as an input side member 71 to which the assist torque of the electric assist motor 50 is input, as shown in FIG. 3, and fixedly couples the input side member 71 to the input shaft 42A of the ball screw 42. The inverse input interrupting apparatus 70 has an output side member 72 from which the assist torque of the assist motor 50 is output, and fixedly couples the output shaft 42B of the ball screw 42 to the output side member 72. The inverse input interrupting apparatus 70 has an outer ring 73A serving as a static side member 73 in which a rotation is constrained, and fixedly couples the static side member 73A to the gear case 41. The inverse input interrupting apparatus 70 has a lock means 74 which is provided between the outer ring 73A of the static side member 73 and the output side member 72, and locks the output side member 72 and the static side member 73 with respect to an inverse input torque from the output side member 72 (a torque given from the inverse input caused by the rotational reaction force of the screw 22 of the outboard motor 20 mentioned above to the output side member 72 via the ball nut 43 and the ball screw 42), and the lock means 74 is constructed by a pair of rollers 74A and 74A provided in a gap of the outer ring 73A and the output side member 72. An N-shaped leaf spring 74B serving as an elastic member applying a force isolating the rollers 74A from each other is interposed between a pair of rollers 74A and 74A. The inverse input interrupting apparatus 70 has an unlocking means 75 which is provided in the input side member 71 and unlocks a lock state by the lock means 74 with respect to the assist torque from the input side member 71, and the unlocking means 75 is constructed by a column portion 71B of the retainer 71A. The inverse input interrupting apparatus 70 has a torque transmitting means 76 which is provided between the input side member 71 and the output side member 72, and transmits the assist torque from the input side member 71 to the output side member 72 at a time of unlocking the lock state by the lock means 74, and the torque transmitting means 76 is constructed by a pin 71C of the retainer 71A. The pin 71C is inserted to a pin hole 72A of the output side member 72, and an inner diameter of the pin hole 72A is made slightly larger than an outer diameter of the pin 71C.

In the inverse input interrupting apparatus 70, when the watercraft steering person loses hold of the steering handle 10 and does not apply a manual steering force, and the assist torque of the assist motor 50 is not applied to the retainer 71A of the input side member 71, the inverse input caused by the rotational reaction force of the screw 22 of the outboard motor 20 is applied to the ball nut 43. As a result, even if the inverse input torque via the output shaft 42B of the ball screw 42 with which the ball nut 43 is engaged is applied to the output side member 72, the roller 74A of the lock means 74 interposed between the output side member 72 and the outer ring 73A of the static side member 73 is engaged with a wedge gap between the output side member 72 and the outer ring 73A of the static side member 73 by the leaf spring 74B so as to be locked, as shown in FIG. 4A. Accordingly, the ball nut 43 is locked immovable and does not steer the propelling unit 21, thereby maintaining a traveling direction of the hull 2 before the steering handle 10 is released.

If the manual steering force is applied to the steering handle 10 as shown in FIG. 4B from the lock state of the output side member 72 and the static side member 73 in FIG. 4A, and the steering torque applied to the steering handle 10, and the assist torque of the assist motor 50 controlled by the control unit 60 are applied to the retainer 71A of the input side member 71, the column portion 71B of the retainer 71A serving as the unlocking means 75 comes into collision with one roller 74A positioned in a rear side of the rotating direction, and presses the roller 74A forward in the rotating direction against the leaf spring 74B. Accordingly, the roller 74A engaging by wedge between the output side member 72 and the outer ring 73A of the static side member 73 breaks away from the wedge gap, and the lock state of the output side member 72 is canceled. Accordingly, the output side member 72 becomes rotatable, as shown in FIG. 4B.

If the retainer 71A of the input side member 71 is further rotated from FIG. 4B, the pin 71C of the input side member 71 comes into collision with an inner diameter surface of the pin hole 72A of the output side member 72 as shown in FIG. 4C, and the torque of the input side member 71 is transmitted to the output side member 72 via the pin 71C, and rotates the output side member 72. Accordingly, the output shaft 42B of the ball screw 42 fixed to the output side member 72 is rotated, and the ball nut 43 engaged with the output shaft 42B of the ball screw 42 is screw movable, thereby steering the propelling unit 21 coupled by the ball nut 43, the links 25A and 25B and the steering arm 21A.

The steering assist apparatus 40 is provided with a torque transmission disconnecting means 80 in an intermediate portion of the steering force transmission path between the inverse input interrupting apparatus 70 and the outboard motor 20, an intermediate portion of the output shaft 42B of the ball screw 42 in the present embodiment, as shown in FIG. 2. The torque transmission disconnecting means 80 is constructed, for example, by a manual clutch, and disconnects the steering force transmission path including the ball nut 43 screw attached to the output shaft 42B of the ball screw 42 with respect to the inverse input interrupting apparatus 70, at a time of a failure of the power steering apparatus 3 when the assist motor 50 and the control unit 60 thereof break down. Accordingly, when the watercraft steering person applies the manual steering force to the steering handle 10, or applies an emergency steering force to the steering arm 21A of the propelling unit 21, the ball screw 42 and the ball nut 43 can screw move regardless of existence of the inverse input interrupting apparatus 70, and can steer the propelling unit 21.

In accordance with the present embodiment, the following operations and effects can be achieved.

(a) There is provided the inverse input interrupting apparatus 70 interrupting the inverse input torque applied to the steering force transmission path from the side of the outboard motor 20 with respect to the assist motor 50, on the basis of the gyro effect caused by the rotational reaction force of the screw 22 provided in the outboard motor 20. Accordingly, when the watercraft steering person loses hold of the steering handle 10 for fishing or the like while the hull 2 is in motion, the inverse input intending to steer the propelling unit 21 on the basis of the gyro effect caused by the rotational reaction force of the screw 22 is interrupted with respect to the assist motor 50 due to the presence of the inverse input interrupting apparatus 70, and the propelling unit 21 can not be steered. Accordingly, the hull 2 can maintain the traveling direction before the watercraft steering person loses hold of the steering handle 10 and thereby, for example, it is possible to maintain a straight traveling performance.

(b) Since the inverse input interrupting apparatus 70 is structured such as to mechanically interrupt the inverse input torque mentioned above with respect to the assist motor 50, and does not lock up against the inverse input torque mentioned above on the basis of the driving force of the electric assist motor, it does not introduce a power consumption and a heat generation, but is simple.

(c) The inverse input interrupting apparatus 70 is constructed by the input side member 71, the output side member 72, the static side member 73, the lock means 74, the unlocking means 75, and the torque transmitting means 76, and can mechanically and securely interrupt the inverse input torque in the item (a) mentioned above with respect to the assist motor 50.

(d) The torque transmission disconnecting means 80 is provided in the intermediate portion of the steering force transmission path between the inverse input interrupting apparatus 70 and the outboard motor 20. Accordingly, the existence of the inverse input interrupting apparatus 70 does not set up against the emergency steering force of the watercraft steering person applied to the propelling unit 21, by disconnecting the steering force transmission path between the inverse input interrupting apparatus 70 and the outboard motor 20, during failure of the assist motor 50 and the control unit 60, and it is possible to freely steer the propelling unit 21.

In this case, the inverse input interrupting apparatus 70 in accordance with the present embodiment may be interposed between the assist motor 50 and the pinion 51.

Embodiment 2 (FIGS. 5 and 6)

A difference between a power steering apparatus 3 of a watercraft 1 in accordance with an embodiment 2 shown in FIGS. 5 and 6 and the embodiment 1 is that the torque sensor 45 and the control unit 60 arranged within the gear case 41 of the steering assist apparatus 40 are moved.

The torque sensor 45 is provided on the handle shaft 11 of the steering handle 10. In other words, the handle shaft 11 is structured such that an input shaft 11A to which the steering handle 10 is directly coupled, is coaxially coupled to an output shaft 11B to which the pinion 12 is directly coupled, via a torsion bar (not shown), and the torque sensor 45 is interposed between the input shaft 11A and the output shaft 11B. Accordingly, the torque sensor 45 is structured such as to detect the steering direction and the steering torque applied by the watercraft steering person to the steering handle 10.

The control unit 60 is arranged on one side of the steering handle 10.

In the present embodiment, the operations and effects (a) to (d) mentioned above of the embodiment 1 can be achieved.

Embodiment 3 (FIG. 7)

A difference between a power steering apparatus 3 of a watercraft 1 in accordance with an embodiment 3 shown in FIG. 7 and the embodiment 1 is that a steering assist apparatus 90 taking the place of the steering assist apparatus 40 is arranged around the steering handle 10 in the bow end in the inner portion of the hull 2.

The steering assist apparatus 90 is arranged within a gear case 91 fixed to the hull 2. The steering assist apparatus 90 is structured such that the handle shaft 11 of the steering handle 10 is separated into two sections including the input shaft 11A to which the steering handle 10 is directly couple, and the output shaft 11B to which the pinion 12 is directly coupled, the input shaft 11A and the output shaft 11B are coaxially coupled via a torsion bar (not shown), and a torque sensor 92 is interposed between the input shaft 11A and the output shaft 11B. The torque sensor 92 detects the steering direction and the steering torque applied by the watercraft steering person to the steering handle 10.

The steering assist apparatus 90 is structured such that an electric assist motor 93 is arranged within the gear case 91, and a worm 94 provided in an output shaft of the assist motor 93 is engaged with a worm wheel 95 provided in the output shaft 11B of the handle shaft 11 of the steering handle 10.

The steering assist apparatus 90 is structured such that a control unit 96 controlling the assist motor 93 is arranged within the gear case 91. The control unit 96 loads a detection signal of the torque sensor 92, and a detection signal of a watercraft speed sensor (not shown) installed in the propelling unit 21 of the outboard motor 20, decides a driving direction and a driving current of the assist motor 93 on the basis of a predetermined assist map, and applies an assist torque of the assist motor 93 which becomes a suitable steering assist force corresponding to the watercraft speed, the steering direction and the steering torque to the output shaft 11B of the handle shaft 11 of the steering handle 10 via the worm 94 and the worm wheel 95. The rotating force of the output shaft 11B caused by the assist torque of the assist motor 93 is structured such as to assist the rotation of the output shaft 11B caused by the steering force of the steering handle 10.

The steering assist apparatus 90 is provided in an output side of the assist motor 93 with an inverse input interrupting apparatus 97 transmitting the assist torque of the assist motor 93 to the steering force transmission path to the propelling unit 21, and interrupting an inverse input torque applied to the steering force transmission path from the side of the propelling unit 21 caused by the rotational reaction force of the screw 22 provided in the propelling unit 21 with respect to the assist motor 93. In the present embodiment, the mechanical inverse input interrupting apparatus 97 is provided in the intermediate portion of the assist motor 93 and the worm 94. The inverse input interrupting apparatus 70 in accordance with the embodiment 1 can be employed as the inverse input interrupting apparatus 97.

The steering assist apparatus 90 can be provided with a torque transmission disconnecting means 98 in the intermediate portion of the inverse input interrupting apparatus 97 and the worm 94. The torque transmission disconnecting means 98 is constructed, for example, by a manual clutch, and disconnects the steering force transmission path including the steering cable 30 with respect to the inverse input interrupting apparatus 97 during failure of the power steering apparatus 3 when the assist motor 93 and the control unit 96 thereof break down. Accordingly, when the watercraft steering person applies the emergency steering force to the steering arm 21A of the propelling unit 21, the steering cable 30 can move regardless the existence of the inverse input interrupting apparatus 97, and can steer the propelling unit 21.

In this case, in the present embodiment, the outboard motor 20 is structured such that the steering cable 30 is directly coupled to the link 25B coupled to the steering arm 21A firmly attached to the propelling unit 21 via the link 25A. In other words, one end of the link 25B is coupled to the steering arm 21A via the link 25A, the other end of the link 25B is guided by the slide guide 26 in such a manner as to linearly movable, and the other end of the steering cable 30 is coupled to the other end of the link 25B.

In accordance with the present embodiment, the following operations and effects can be achieved.

(a) There is provided the inverse input interrupting apparatus 97 interrupting the inverse input torque applied to the steering force transmission path from the side of the outboard motor 20 with respect to the assist motor 93, on the basis of the gyro effect caused by the rotational reaction force of the screw 22 provided in the outboard motor 20. Accordingly, when the watercraft steering person loses hold of the steering handle 10 for fishing or the like while the hull 2 is in motion, the inverse input intending to steer the propelling unit 21 on the basis of the gyro effect caused by the rotational reaction force of the screw 22 is interrupted with respect to the assist motor 93 due to the existence of the inverse input interrupting apparatus 97, and the propelling unit 21 can not be steered. Accordingly, the hull 2 can maintain the traveling direction before the watercraft steering person loses hold of the steering handle 10 and thereby, for example, it is possible to maintain a straight traveling performance.

(b) Since the inverse input interrupting apparatus 97 is structured such as to mechanically interrupt the inverse input torque mentioned above with respect to the assist motor 93, and does not set up against the inverse input torque mentioned above on the basis of the driving force of the electric assist motor, it does not introduce a power consumption and a heat generation, but is simple.

(c) The inverse input interrupting apparatus 97 is constructed by the input side member 71, the output side member 72, the static side member 73, the lock means 74, the unlocking means 75, and the torque transmitting means 76, and can mechanically and securely interrupt the inverse input torque in the item (a) mentioned above with respect to the assist motor 93.

(d) The torque transmission disconnecting means 98 is provided in the intermediate portion of the steering force transmission path between the inverse input interrupting apparatus 97 and the outboard motor 20. Accordingly, the existence of the inverse input interrupting apparatus 97 does not set up against the emergency steering force of the watercraft steering person applied to the propelling unit 21, by disconnecting the steering force transmission path between the inverse input interrupting apparatus 97 and the outboard motor 20, during failure of the assist motor 93 and the control unit 96, and it is possible to freely steer the propelling unit 21.

Embodiment 4 (FIGS. 8 to 9)

A watercraft 1 shown in FIG. 8 has a steering handle 10 provided in a bow end of a hull 2, an outboard motor 20 serving as a propeller provided in a stern end of the hull 2, and a steering cable 30 serving as a steering force transmission path transmitting a steering force applied to the steering handle 10 to the outboard motor 20. The steering cable 30 is extended within an outer tube 31 installed in the stern end from the bow end in an inner portion of the hull 2.

The steering handle 10 is installed in a control seat in the bow end of the hull 2. A pinion 12 fixed to a handle shaft 11 of the steering handle 10 is engaged with a rack 13, and the rack 13 is coupled to one end of the steering cable 30. The steering handle 10 is rotated leftward or rightward on the basis of an application of a steering force (a steering torque), whereby the steering cable 30 is pushed and pulled via an engagement between the pinion 12 and the rack 13.

The outboard motor 20 is provided with a screw 22 in a propelling unit 21, and is structured such as to have an engine (not shown) mounted on the propelling unit 21, and a swivel bracket 23 and a clamp bracket 24. The propelling unit 21 is pivoted to a swivel bracket 23 via a steering shaft (not shown) so as to oscillate in a horizontal direction and be capable of steering, and the swivel bracket 23 is pivoted to the clamp bracket 24 so as to be tiltable up and down in a vertical direction via a tilt shaft (not shown). The outboard motor 20 is attached to a stern plate of the hull 2 by the clamp bracket 24, transmits an output of the engine to the screw 22, and makes the hull 2 movable forward and backward. The outboard motor 20 couples the other end of the steering cable 30 to a steering arm 21A firmly attached to the propelling unit 21 via links 25A and 25B.

In the watercraft 1, a steering assist apparatus 40 for constructing a power steering apparatus 3 assisting a steering force applied by a watercraft steering person to the steering handle 10 is interposed between the other end of the steering cable 30 and the steering arm 21A (the link 25B in the present embodiment) of the propelling unit 21, in the stern end in the inner portion of the hull 2.

The steering assist apparatus 40 is arranged within a gear case 41 fixed to the hull 2, as shown in FIG. 9. The steering assist apparatus 40 is structured such that the input shaft 42 and the output shaft 43 are coaxially coupled via a torsion bar (not shown), and the input shaft 42 and the output shaft 43 are pivoted to the gear case 41. The rack 45 coupled to the other end of the steering cable 30 is engaged with the pinion 44 fixed to the input shaft 42, and the rack 45 is slidably supported to the gear case 41. The rack 47 is engaged with the pinion 46 fixed to the output shaft 43, and the rack 47 is slidably supported to the gear case 41. The link 25B coupled to the propelling unit 21 via the steering arm 21A and the link 25A is coupled to one end of the rack 47. Accordingly, if the steering handle 10 is rotated leftward or rightward on the basis of the application of the steering force, the cable 30 is pushed and pulled, the rack 45 is linearly moved, the input shaft 42 and the output shaft 43 are rotated on the basis of the engagement between the rack 45 and the pinion 44, and the rack 47 is pushed and pulled on the basis of the engagement between the pinion 46 and the rack 47 in the output shaft 43. As a result, the propelling unit 21 coupled to the rack 47 via the links 25B and 25A and the steering arm 21A is steered leftward or rightward.

The steering assist apparatus 40 is structured such that the torque sensor 48 is interposed between the input shaft 42 and the output shaft 43 within the gear case 41. The torque sensor 48 detects the steering direction and the steering torque applied by the watercraft steering person to the steering handle 10.

The steering assist apparatus 40 is structured such that the electric assist motor 50 is arranged within the gear case 41. The steering assist apparatus 40 interposes a worm reduction gear 60 constructed by engaging a worm 61 provided in the output shaft of the assist motor 50 with a worm wheel 62 provided in the output shaft 43 in a side of the outboard motor 20, in the steering force transmission path in the output side of the assist motor 50.

The steering assist apparatus 40 is structured such that a control unit 70 controlling the assist motor 50 is arranged within the gear case 41. The control unit 70 loads a detection signal of the torque sensor 48, and a detection signal of a watercraft speed sensor (not shown) installed in the propelling unit 21 of the outboard motor 20, decides a driving direction and a driving current of the assist motor 50 from a predetermined assist map, and applies a motor torque of the assist motor 50 which becomes a suitable steering assist force corresponding to the watercraft speed, the steering direction and the steering torque to the output shaft 43 via the worm 61 and worm wheel 62.

The steering assist apparatus 40 constructs an inverse input interrupting apparatus 60A by the worm reduction gear 60 (the worm 61 and the worm wheel 62). The inverse input interrupting apparatus 60A of the worm reduction gear 60 sets up against the inverse input applied to the output shaft 43 via the steering arm 21 from the side of the propelling unit 21 on the basis of the rotational reaction force of the screw 22 of the outboard motor 20. In other words, the worm reduction gear 60 generates a self-lock making it impossible to rotate the worm 61 from the worm wheel 62, by setting a lead angle γ of the worm 61 (a torsion angle of the worm wheel 62) smaller than an additional value (θ+θ1) of a friction angle θ (θ=tan−1 η) caused by a friction coefficient η of a tooth surface of the worm 61 and the worm wheel 62, and a friction angle θ1 caused by a friction coefficient η around a bearing of the worm 61 and the assist motor 50 (γ≦θ+θ1), and locks the rotation of the output shaft 43 at a time when the inverse input mentioned above is applied to the output shaft 43 from the side of the propelling unit 21. Accordingly, the inverse input interrupting apparatus 60A of the worm reduction gear 60 holds back the rotation of the output shaft 43 with respect to the inverse input mentioned above, and allows the rotation of the output shaft 43 generated by the manual steering torque applied to the steering cable 30 or the motor torque of the assist motor 50.

5 Further, the steering assist apparatus 40 is provided with the torque transmission disconnecting means 80 in the steering force transmission path between the worm reduction gear 60 and the outboard motor 20, for example, in the intermediate portion of the output shaft 43. The torque transmission disconnecting means 80 is constructed, for example, by a manual clutch, and disconnects the steering force transmission path in the side of the propelling unit 21 including the pinion 46 with respect to the worm wheel 60, at a time of failure of the power steering apparatus 3 when the assist motor 50 and the control unit 70 thereof break down. Accordingly, when the watercraft steering person applies the emergency steering force to the steering arm 21A of the propelling unit 21, the pinion 46 and the rack 47 can move regardless of the existence of the worm reduction gear 60 (the inverse input interrupting apparatus 60A), and it is possible to lightly steer the propelling unit 21.

In accordance with the present embodiment, the following operations and effects can be obtained.

(a) The worm reduction gear 60 is interposed in the steering force transmission path in the output side of the assist motor 50, the worm reduction gear 60 being formed by engaging the worm 61 provided in the side of the assist motor 50, with the worm wheel 62 provided in the side of the outboard motor 20. Further, the inverse input interrupting apparatus 60A is constructed by the self-lock mechanism of the worm reduction gear 60, the inverse input interrupting apparatus 60A interrupting the inverse input torque applied to the steering force transmission path from the side of the outboard motor 20 with respect to the assist motor 50, on the basis of the gyro effect caused by the rotational reaction force of the screw 22 provided in the outboard motor 20. Accordingly, when the watercraft steering person loses hold of the steering handle 10 for fishing or the like while the hull 2 is in motion, the inverse input torque intending to steer the propelling unit 21 on the basis of the gyro effect caused by the rotational reaction force of the screw 22 is interrupted with respect to the assist motor 50 on the basis of the existence of the inverse input interrupting apparatus 60A of the worm reduction gear 60, and the propelling unit 21 can not be steered. Therefore, the hull 2 can maintain the traveling direction before the watercraft steering person loses hold of the steering handle 10, and for example, it is possible to maintain a straight going performance.

(b) Since the inverse input interrupting apparatus 60A of the worm reduction gear 60 is structured such as to mechanically interrupt the inverse input torque mentioned above with respect to the assist motor 50, and does not set up against the inverse input torque mentioned above on the basis of the driving force of the electric assist motor 50, it does not introduce a power consumption and a heat generation, but is simple.

(c) The torque transmission disconnecting means 80 is provided in the intermediate portion of the steering force transmission path between the worm reduction gear 60 and the outboard motor 20. Accordingly, the existence of the worm reduction gear 60 does not set up against the emergency steering force of the watercraft steering person applied to the propelling unit 21 at all, by disconnecting the steering force transmission path between the worm reduction gear 60 and the outboard motor 20 when the assist motor 50 and the control unit 70 thereof break down, and it is possible to freely steer the propelling unit 21.

Embodiment 5 (FIGS. 10 and 11)

A difference between a power steering apparatus 3 of a watercraft 1 in accordance with an embodiment 5 shown in FIGS. 10 and 11 and the embodiment 4 is that the torque sensor 48 and the control unit 70 arranged within the gear case 41 of the steering assist apparatus 40 are moved.

The torque sensor 48 is provided on the handle shaft 11 of the steering handle 10. In other words, the handle shaft 11 is structured such that the input shaft 11A to which the steering handle 10 is directly coupled is coaxially coupled to the output shaft 11B to which the pinion 12 is directly coupled via a torsion bar (not shown), and the torque sensor 48 is interposed between the input shaft 11A and the output shaft 11B. Accordingly, the torque sensor 48 is structured such as to detect the steering direction and the steering torque applied by the watercraft steering person to the steering handle 10.

The control unit 70 is arranged on one side of the steering handle 10.

Further, in the embodiment 5, the other end of the steering cable 30 is directly coupled to the rack 47 via the coupling bar 32, by setting the torque sensor 48 in the intermediate portion of the handle shaft 11. The coupling bar 32 is guided in such a manner as to be slidable along an axial direction of the rack 47. The output shaft 43 is provided with the worm wheel 62 of the worm reduction gear 60 (the inverse input interrupting apparatus 60A) to which the output shaft of the assist motor 50 is connected, and the worm wheel 62 is engaged with the rack 47 of the pinion 46 of the output shaft 43 in the same manner as the embodiment 4. The torque transmission disconnecting means 80 may be provided in the intermediate portion of the output shaft 43. The torque transmission disconnecting means 80 is constructed, for example, by a manual clutch, and disconnects the steering force transmission path in the side of the propelling unit 21 including the pinion 46 with respect to the worm wheel 62, at a time of failure of the power steering apparatus 3 when the assist motor 50 and the control unit 70 thereof break down. Accordingly, when the watercraft steering person applies the steering force to the steering handle 10, the pinion 46 and the rack 47 can move regardless of the existence of the worm reduction gear 60 (the inverse input interrupting apparatus 60A), and it is possible to lightly steer the propelling unit 21.

In the present embodiment, the operations and effects (a) and (b) mentioned above of the embodiment 4 can be achieved.

Embodiment 6 (FIG. 12)

A difference between a power steering apparatus 3 of a watercraft 1 in accordance with an embodiment 6 shown in FIG. 12 and the embodiment 4 is that a steering assist apparatus 90 taking the place of the steering assist apparatus 40 is arranged around the steering handle 10 in the bow end in the inner portion of the hull 2.

The steering assist apparatus 90 is arranged within a gear case 91 fixed to the hull 2. The steering assist apparatus 90 is structured such that the handle shaft 11 of the steering handle 10 is separated into two sections including the input shaft 11A to which the steering handle 10 is directly coupled, and the output shaft 11B to which the pinion 12 is directly coupled, the input shaft 11A and the output shaft 11B are coaxially coupled via a torsion bar (not shown), and a torque sensor 92 is interposed between the input shaft 11A and the output shaft 11B. The torque sensor 92 detects the steering direction and the steering torque applied by the watercraft steering person to the steering handle 10.

Further, the steering assist apparatus 90 is structured such that an electric assist motor 93 is arranged within the gear case 91, and a worm 101 provided in an output shaft of the assist motor 93 is engaged with a worm wheel 102 provided in the output shaft 11B of the handle shaft 11 of the steering handle 10. The worm 101 and the worm wheel 102 construct the worm reduction gear 100 taking the place of the worm reduction gear 60 in accordance with the embodiment 4.

Further, the steering assist apparatus 90 is structured such that a control unit 110 controlling the assist motor 93 is arranged within the gear case 91. The control unit 110 loads a detection signal of the torque sensor 92, and a detection signal of a watercraft speed sensor (not shown) installed in the propelling unit 21 of the outboard motor 20, decides a driving direction and a driving current of the assist motor 93 on the basis of a predetermined assist map, and applies an assist torque of the assist motor 93 which becomes a suitable steering assist force corresponding to the watercraft speed, the steering direction and the steering torque to the output shaft 11B of the handle shaft 11 of the steering handle 10 via the worm 101 and the worm wheel 102. The rotating force of the output shaft 11B caused by the assist torque of the assist motor 93 is structured such as to assist the rotation of the output shaft 11B caused by the steering force of the steering handle 10.

The steering assist apparatus 90 constructs an inverse input interrupting apparatus 100A by the worm reduction gear 100 (the worm 101 and the worm wheel 102). The inverse input interrupting apparatus 100A holds back the rotation of the handle shaft 11 with respect to the inverse input applied to the steering cable 30 from the side of the propelling unit 21 caused by the reaction force of the rotation of the screw 22 provided in the outboard motor 20, and allows the rotation of the handle shaft 11 generated by the manual steering torque applied to the steering handle 10 or the motor torque of the assist motor 93.

Further, the steering assist apparatus 90 can be provided with a torque transmission disconnecting means 120 in the steering force transmission path between the worm reduction gear 100 and the outboard motor 20, for example, in the intermediate portion of the output shaft 11B of the handle shaft 11. The torque transmission disconnecting means 120 is constructed, for example, by a manual clutch, and disconnects the steering force transmission path in the side of the propelling unit 21 including the pinion 12 with respect to the worm wheel 102, during failure of the power steering apparatus 3 when the assist motor 93 and the control unit 110 break down. Accordingly, when the watercraft steering person applies the emergency steering force to the steering arm 21A of the propelling unit 21, the pinion 12 and the rack 13 can move regardless of the existence of the worm reduction gear 100 (the inverse input disconnecting apparatus 100A), and it is possible to lightly steer the propelling unit 21.

In this case, in the present embodiment, the outboard motor 20 is structured such that the steering cable 30 is directly coupled to the link 25B coupled to the steering arm 21A firmly attached to the propelling unit 21 via the link 25A. In other words, one end of the link 25B is coupled to the steering arm 21A via the link 25A, the other end of the link 25B is guided by the slide guide 26 in such a manner as to linearly movable, and the other end of the steering cable 30 is coupled to the other end of the link 25B.

In accordance with the present embodiment, the following operations and effects can be achieved.

(a) The worm reduction gear 100 is interposed in the steering force transmission path in the output side of the assist motor 93, the worm reduction gear 100 being formed by engaging the worm 101 provided in the side of the assist motor 93, with the worm wheel 102 provided in the side of the outboard motor 20. Further, the inverse input interrupting apparatus 100A is constructed by the self-lock mechanism of the worm reduction gear 100, the inverse input interrupting apparatus 100A interrupting the inverse input torque applied to the steering force transmission path from the side of the outboard motor 20 with respect to the assist motor 93, on the basis of the gyro effect caused by the rotational reaction force of the screw 22 provided in the outboard motor 20. Accordingly, when the watercraft steering person loses hold of the steering handle 10 for fishing or the like while the hull 2 is in motion, the inverse input torque intending to steer the propelling unit on the basis of the gyro effect caused by the rotational reaction force of the screw 22 is interrupted with respect to the assist motor 93 on the basis of the existence of the inverse input interrupting apparatus 100A of the worm reduction gear 100, and the propelling unit can not be steered. Therefore, the hull 2 can maintain the traveling direction before the watercraft steering person loses hold of the steering handle 10, and for example, it is possible to maintain a straight going performance.

(b) Since the inverse input interrupting apparatus 100A of the worm reduction gear 100 is structured to mechanically interrupt the inverse input torque mentioned above with respect to the assist motor 93, and does not set up against the inverse input torque mentioned above on the basis of the driving force of the electric assist motor, it does not introduce a power consumption and a heat generation, but is simple.

As heretofore explained, embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configurations of the present invention are not limited to the illustrated embodiments but those having a modification of the design within the range of the presently claimed invention are also included in the present invention. For example, in accordance with the present invention, the torque transmission disconnecting means may be provided in the intermediate portion of the steering force transmission path between the assist driving portion and the propeller, in the power steering apparatus of the watercraft with propeller applying the assist torque of the assist driving portion driven in correspondence to the steering direction and the steering force of the steering handle to the steering force transmission path to the propeller.

Although the invention has been illustrated and described with respect to several exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made to the present invention without departing from the spirit and scope thereof. Therefore, the present invention should not be understood as limited to the specific embodiment set out above, but should be understood to include all possible embodiments which can be encompassed within a scope of equivalents thereof with respect to the features set out in the appended claims. 

1. A power steering apparatus of a watercraft with propeller for applying an assist torque from an assist driving portion driven in correspondence to a steering direction and a steering force of a steering handle to a steering force transmission path to the propeller, wherein the apparatus is provided with an inverse input interrupting apparatus; the inverse input interrupting apparatus transmitting the torque assisting a steering generated by the assist driving portion to the steering force transmission path, and interrupting a torque applied to the steering force transmission path from a propeller side.
 2. A power steering apparatus of a watercraft with propeller as claimed in claim 1, wherein said inverse input disconnecting apparatus comprises an input side member to which the assist torque of the assist driving portion is input, an output side member from which said assist torque is output, a locking means constructed by a static side member in which a rotation is constrained, provided between the static side member and the output side member, and locking the output side member and the static side member with respect to the inverse input torque from the output side member, an unlocking means provided in the input side member and unlocking a lock state by the lock means with respect to the assist torque from the input side member, and a torque transmitting means provided between the input side member and the output side member, and transmitting the assist torque from the input side member to the output side member at a time of unlocking the lock state by the locking means.
 3. A power steering apparatus of a watercraft with propeller as claimed in claim 2, wherein a torque transmission disconnecting means is provided between an intermediate portion of the steering force transmission path between said inverse input interrupting apparatus and the propeller.
 4. A power steering apparatus of a watercraft with propeller applying an assist torque of an assist driving portion driven in correspondence to a steering direction and a steering force of a steering handle to a steering force transmission path to the propeller, wherein a torque transmission disconnecting means is provided in an intermediate portion of the steering force transmission path between the assist driving portion and the propeller.
 5. A power steering apparatus of a watercraft with propeller applying an assist torque of an assist driving portion driven in correspondence to a steering direction and a steering force of a steering handle to a steering force transmission path to the propeller, wherein a worm reduction gear is interposed in the steering force transmission path in an output side of the assist driving portion, the worm reduction gear being formed by engaging a worm provided in a side of the assist driving portion, and a worm wheel provided in a side of the propeller, and an inverse input interrupting apparatus is constructed by the worm reduction gear, the inverse input interrupting apparatus transmitting the assist torque of the assist driving portion to the side of the propeller, and interrupting an inverse input torque applied to the steering force transmission path from the side of the propeller caused by a rotational reaction force of a screw provided in the propeller with respect to the assist driving portion.
 6. A power steering apparatus of a watercraft with propeller as claimed in claim 5, wherein a torque transmission disconnecting means is provided in an intermediate portion of the steering force transmission path between said worm reduction gear and the propeller. 